Observer-based robust high-order fully actuated attitude autopilot design for spinning glide-guided projectiles

This paper investigates the design of an attitude autopilot for a dual-channel controlled spinning glideguided projectile(SGGP),addressing model uncertainties and external disturbances.Based on fixed-time stable theory,a disturbance observer with integral sliding mode and adaptive techniques is proposed to mitigate total disturbance effects,irrespective of initial conditions.By introducing an error integral signal,the dynamics of the SGGP are transformed into two separate second-order fully actuated systems.Subsequently,employing the high-order fully actuated approach and a parametric approach,the nonlinear dynamics of the SGGP are recast into a constant linear closed-loop system,ensuring that the projectile's attitude asymptotically tracks the given goal with the desired eigenstructure.Under the proposed composite control framework,the ultimately uniformly bounded stability of the closed-loop system is rigorously demonstrated via the Lyapunov method.Validation of the effectiveness of the proposed attitude autopilot design is provided through extensive numerical simulations.

High-order sliding mode attitude controller design for reentry flight

A novel high-order sliding mode control strategy is proposed for the attitude control problem of reentry vehicles in the presence of parametric uncertainties and external disturbances, which results in the robust and accurate tracking of the aerodynamic angle commands with the finite time convergence. The proposed control strategy is developed on the basis of integral sliding mode philosophy, which combines conventional sliding mode control and a linear quadratic regulator over a finite time interval with a free-final-state and allows the finite-time establishment of a high-order sliding mode. Firstly, a second-order sliding mode attitude controller is designed in the proposed high-order siding mode control framework. Then, to address the control chattering problem, a virtual control is introduced in the control design and hence a third-order sliding mode attitude controller is developed, leading to the chattering reduction as well as the control accuracy improvement. Finally, simulation examples are given to illustrate the effectiveness of the theoretical results.

Solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain

By use of the Hartree approximation and the method of multiple scales, we investigate quantum solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain. It is shown that there exist solitons of two different quantum frequency bands： i.e., magnetic optical solitons and acoustic solitons. At the boundary of the Brillouin zone, these solitons becornc quantum intrinsic localized modes： their quantum eigenfrequencics are below the bottom of the harmonic optical frequency band and above the top of the harmonic acoustic frequency band.

Fast self-adapting high-order sliding mode control for a class of uncertain nonlinear systems

A fast self-adapting high-order sliding mode(FSHOSM)controller is designed for a class of nonlinear systems with unknown uncertainties.As for uncertainty-free nonlinear system,a new switching condition is introduced into the standard geometric homogeneity.Different from the existing geometric homogeneity method,both state variables and their derivatives are considered to bring a reasonable effective switching condition.As a result,a faster convergence rate of state variables is achieved.Furthermore,based on the integral sliding mode(ISM)and above geometric homogeneity,a self-adapting high-order sliding mode(HOSM)control law is proposed for a class of nonlinear systems with uncertainties.The resulting controller allows the closed-loop system to conduct with the expected properties of strong robustness and fast convergence.Stable analysis of the nonlinear system is also proved based on the Lyapunov approach.The effectiveness of the resulting controller is verified by several simulation results.

Internal mode of incoherent photovoltaic vector solitons

The internal modes of incoherent vector solitons （IVSs） in photovoltaic photorefractive materials are investigated in the framework of coupled nonlinear Schrodinger equations. It is found that there is a pair of internal modes corresponding to a bright-bright IVS. The propagation dynamics of the bright-bright IVS perturbed by the internal modes is simulated by numerical method.

Quantum Solitons and Localized Modes in a One-Dimensional Lattice Chain with Nonlinear Substrate Potential

In the classical lattice theory, solitons and localized modes can exist in many one-dimensional nonlinear lattice chains, however, in the quantum lattice theory, whether quantum solitons and localized modes can exist or not in the one-dimensional lattice chains is an interesting problem. By using the number state method and the Hartree approximation combined with the method of multiple scales, we investigate quantum solirons and localized modes in a one-dimensional lattice chain with the nonlinear substrate potential. It is shown that quantum solitons do exist in this nonlinear lattice chain, and at the boundary of the phonon Brillouin zone, quantum solitons become quantum localized modes, phonons are pinned to the lattice of the vicinity at the central position j = j0.

Laser shaping and optical power limiting of pulsed Laguerre–Gaussian laser beams of high-order radial modes in fullerene C60

We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre–Gaussian laser beam is strongly reshaped during its propagation in the C60molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a noncentrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre–Gaussian laser beams before the takeover of the saturation effect;the lower the order of the Laguerre–Gaussian beam, the lower the energy transmittance.

Soliton fusion and fission for the high-order coupled nonlinear Schr?dinger system in fiber lasers

With the rapid development of communication technology,optical fiber communication has become a key research area in communications.When there are two signals in the optical fiber,the transmission of them can be abstracted as a high-order coupled nonlinear Schr¨odinger system.In this paper,by using the Hirota’s method,we construct the bilinear forms,and study the analytical solution of three solitons in the case of focusing interactions.In addition,by adjusting different wave numbers for phase control,we further discuss the influence of wave numbers on soliton transmissions.It is verified that wave numbers k_(11),k_(21),k_(31),k_(22),and k_(32)can control the fusion and fission of solitons.The results are beneficial to the study of all-optical switches and fiber lasers in nonlinear optics.

Integrated of Proximity-Coupling High-Order Modes Patch Antenna with Solar Cells for Sustainable Communication

An integration of single-layer proximitycoupling patch antenna and solar cells with bandwidth enhancement and optical energy harvesting is proposed for sustainable communication.For this purpose,many dual-function components are selected for designing the miniaturized solar cell antenna.On the one hand,by greatly affecting the current flow of the rectangular patch,vias and proximity-coupling are introduced to control the resonance modes frequency and matching,respectively,for wideband application,and the radiation performance property can be achieved by high-order mode.On the other hand,vias and proximity-coupling are beneficial to complete direct-current(DC)loop of solar cell and improve compatibility of DC-RF(radio frequency),whereas a high-order mode is beneficial to increase the area of collected light energy.To prove the working principle,fabricated and manufactured solar cell antenna.The measured and simulated results illustrate that the solar cell antenna gain is raised to as high as 9.27 d Bi in4.37 to 5.06 GHz applied to fifth generation communication(5G).

Micro-Sized Pinhole Inspection with Segmented Time Reversal and High-Order Modes Cluster Lamb Waves Based on EMATs

Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.

High-Order Lateral Buckling Analysis of Submarine Pipeline Under Thermal Stress

It is of importance to study and predict the possible buckling of submarine pipeline under thermal stress in pipeline design.Since soil resistance is not strong enough to restrain the large deformation of pipeline,high-order buckling modes occur very easily.Analytical solutions to high-order buckling modes were obtained in this paper.The relationships between buckling temperature and the amplitude or the wavelength of buckling modes were established.Analytical solutions were obtained to predict the occurrence and consequence of in-service buckling of a heated pipeline in an oil field.The effects of temperature difference and properties of subsoil on buckling modes were investigated.The results show that buckling will occur once temperature difference exceeds safe temperature;high-order pipeline buckling occurs very easily;the larger the friction coefficients are,the safer the submarine pipeline will be.

Bound soliton pulses in a passively mode-locked fibre ring laser

The bound solitons in a passively mode-locked fibre ring laser are observed and their formation mechanism is summarized in this paper. In order to obtain stable bound solitons, a strong CW laser field at the centre of the soliton spectral is necessary to suppress and synchronize the random soliton phase variations.

Signature of Different Phases of Ricci Flat Black Holes and AdS Solitons in Gauss-Bonnet Gravity

From the perturbation around the background spacetimes in the Gauss Bonnet gravity, we find the physical evidence that Ricci fiat AdS black holes and AdS solitons are different physical configurations and stay in different phases, this serves as a strong support to the previous mathematical and thermodynamieal arguments.

Observation of stable bound soliton with dual-wavelength in a passively mode-locked Er-doped fiber laser

A phase-locked bound state soliton with dual-wavelength is observed experimentally in a passively mode-locked Erdoped fiber（EDF） laser with a fiber loop mirror（FLM）. The pulse duration of the soliton is 15 ps and the peak-to-peak separation is 125 ps. The repetition rate of the pulse sequence is 3.47 MHz. The output power is 11.8 mW at the pump power of 128 mW, corresponding to the pulse energy of 1.52 nJ. The FLM with a polarization controller can produce a comb spectrum, which acts as a filter. By adjusting the polarization controller or varying the pump power, the central wavelength of the comb spectrum can be tuned. When it combines with the reflective spectrum of the fiber Bragg grating, the total spectrum of the cavity can be cleaved into two parts, then the bound state soliton with dual-wavelength at 1549.7 nm and 1550.4 nm is obtained.

Soliton evolution and control in a two-mode fiber with two-photon absorption

Soliton dynamics are numerically investigated in a two-mode fiber with the two-photon absorption,and the effects of the two-photon absorption on the soliton propagation and interaction are demonstrated in different dispersion regimes.Soliton dynamics depend strictly on the sign and magnitude of the group velocity dispersion(GVD)coefficient of each mode and the strength(coefficient)of the two-photon absorption.The two-photon absorption leads to the soliton collapse,enhances the neighboring soliton interaction in both modes,and increases the energy exchange between the two modes.Finally,an available control is proposed to suppress the effects by the use of the nonlinear gain with filter.

On the generation of high-quality Nyquist pulses in mode-locked fiber lasers

Nyquist pulses have wide applications in many areas,from electronics to optics.Mode-locked lasers are ideal platforms to generate such pulses.However,how to generate high-quality Nyquist pulses in mode-locked lasers remains elusive.We address this problem by managing different physical effects in mode-locked fiber lasers through extensive numerical simulations.We find that net dispersion,linear loss,gain and filter shaping can affect the quality of Nyquist pulses significantly.We also demonstrate that Nyquist pulses experience similariton shaping due to the nonlinear attractor effect in the gain medium.Our work may contribute to the design of Nyquist pulse sources and enrich the understanding of pulse shaping dynamics in mode-locked lasers.

Generation of tunable high-order Laguerre– Gaussian petal-like modes from a mid-infrared optical vortex parametric oscillator

High-order Laguerre–Gaussian(LG)petal-like beams have become a topic of significant interest due to their potential application in next-generation optical trapping,quantum optics,and materials processing technologies.In this work,we demonstrate the generation of high-order LG beams with petal-like spatial profiles and tunable orbital angular momentum(OAM)in the mid-infrared wavelength region.These beams are generated using idler-resonant optical parametric oscillation(OPO)in a KTiOAsO_(4)(KTA)crystal.By adjusting the length of the resonant cavity,the OAM of the mid-infrared idler field can be tuned and we demonstrate tuning in the range of 0 to
10.When using a maximum pump energy of 20.2 mJ,the maximum output energy of high-order modes LG_(0.45),LG_(0.48),and LG_(0.410) were 0.8,0.53,and 0.46 mJ,respectively.The means by which high-order LG modes with petal-like spatial profiles and tunable OAM were generated from the OPO is theoretically modeled by examining the spatial overlap efficiency of the beam waists of the pump and resonant idler fields within the center of the KTA crystal.The methodology presented in this work offers a simple and flexible method to wavelength-convert laser emission and generate high-order LG modes.

High-order Soliton Matrix for the Third-order Flow Equation of the Gerdjikov-Ivanov Hierarchy Through the Riemann-Hilbert Method

The Gerdjikov-Ivanov(GI)hierarchy is derived via recursion operator,in this article,we mainly investigate the third-order flow GI equation.In the framework of the Riemann-Hilbert method,the soliton matrices of the third-order flow GI equation with simple zeros and elementary high-order zeros of Riemann-Hilbert problem are constructed through the standard dressing process.Taking advantage of this result,some properties and asymptotic analysis of single soliton solution and two soliton solution are discussed,and the simple elastic interaction of two soliton are proved.Compared with soliton solution of the classical second-order flow,we find that the higher-order dispersion term affects the propagation velocity,propagation direction and amplitude of the soliton.Finally,by means of a certain limit technique,the high-order soliton solution matrix for the third-order flow GI equation is derived.

Pulse-train nonuniformity in an all-fiber ring laser passively mode-locked by nonlinear polarization rotation

This paper reports the periodic power variation of the pulse-train in a passively mode-locked soliton fiber ring laser. It can obtain either the uniform or nonuniform pulse-train output by simply rotating the polarization controllers. The experimental results show that the pulse-train nonuniformity is caused by the interaction between the nonuniform polarization states of the soliton pulses and the passive polarizer in the cavity.

Optical Pulse Compression Based on High-doped Erbium Fiber Amplifier and Standard Single-mode Fiber

Proposed is a novel optical pulse compression technique based on high-doped erbium fiber amplifier and standard single-mode fiber(SMF). We used the amplifier with the erbium ion concentration of 6.3×10-3 to amplify a hyperbolic secant pulse from a regeneratively mode-locked fiber laser. The central wavelength, pulsewidth and peak power of the pulse are 1 550 nm, 12.5 ps and 3 mW, respectively. Then the amplified pulse with peak power level corresponding to a higher-order soliton is compressed when it propagates through a 3-km-long single-mode fiber. Studied are the compressed pulses under different pump powers and fiber lengths. The results show that it can get a narrower pulse, and solve the difficulty that pulses at low power can not be compressed directly in the fiber. And the construct is compact.